Hybrid Electric Tool Carrier

ABSTRACT

A hybrid utility vehicle includes a tool-supporting frame and an electrical power source driven by an engine. Right and left rear wheels independently driven by permanent magnet electric motors and front wheels electrically steerable over a range of approximately 180 degrees operate under the control of a vehicle controller responsive to steering and speed input controls to provide zero turn radius operation with minimum slippage and tire scuffing. Space efficiency provided by the electric. steering and an electrically driven tool deck facilitate a variety of tool mounting configurations including a rear discharge deck with a chute passing under the vehicle frame between the driven wheels. An inverter connected to the electrical power source provides 110/220 volt output. The power source also functions as a high powered, high rpm, low noise starter motor.

FIELD OF THE INVENTION

The present invention relates generally to utility vehicles and morespecifically to off-road hybrid electric vehicles such as lawn andgarden tractors.

BACKGROUND OF THE INVENTION

Off-road utility vehicles such as garden tractors typically include abasic carrier unit with an internal combustion engine and electricalpower source. The carrier unit is powered by the engine, either througha direct mechanical drive or a hydraulic drive, or indirectly throughthe electrical power supply and one or more electric traction motors.

The carrier unit accepts various selectively replaceable attachmentswhich are powered by the engine and/or electrical source. For example, ariding lawn mower includes a deck supported under a vehicle frame.Usually the cut material discharge chute is located on the side of thedeck, and therefore the ability to trim on either side of the machine islimited. Some rear discharge machines have chutes which pass over a rearframe portion and transmission for directing cut material into a hopper.For example, U.S. Pat. No. 6,631,607 shows a rear discharge chute whichdirects cut material over a pair of hydrostatic transmissions. Avoidinginterference with drive transmission structure prevents optimization ofrear discharge chute size and configuration, and most rear chutes have asmaller capacity than that necessary for optimum machine productivity.

Conventional transmissions for riding mowers and similar utilityvehicles often require a differential lock for maximum traction.However, when making tight turns, such as when mowing around a tree,wheel slip will cause tire scuffing and will tear up turf.

Vehicles having front caster wheels and independently drivable rearwheels provide zero turn radius maneuverability and eliminate most wheelslip. By driving one drive wheel forwardly while driving the other inreverse, a spin turn maneuver may be accomplished. Zero turn radiusvehicles are sometimes uncomfortable for some first time users tooperate, and operation on slopes can be difficult with the front casterwheel construction. Many people prefer a positive front wheel steerarrangement with a conventional steering wheel. Commonly assigned U.S.Pat. No. 6,454,032 shows a drive and steer type of arrangement providingautomotive type of controls which are more comfortable to mostconsumers, but positive front wheel steer for better control on slopesis lacking. It is desirable to provide a front wheel steer option forutility vehicles with control that can be easily incorporated into thevehicle electronic controller. The rear wheels should be capable ofsteering the vehicle by driving when the front wheel steer option isdisabled or not selected. On start-up of the vehicle, the position ofthe steered front wheels should be ascertainable.

For compact, high power drive arrangement in hostile environments suchas encountered by lawn and garden tractors and other utility vehicles,brushless permanent magnet direct current (PMDC) motors and permanentmagnet electrical power generators are available. With permanent magnetgenerators, the option to vary field current and thus the magnetic fluxto vary output voltage is unavailable. Driving the generator atdifferent speeds causes considerable variation in the output voltage. Toprovide sufficient operating voltage, the generator must either be woundfor sufficient voltage at low engine speed which results in highover-voltage at full engine speed, or be wound for high speeds whichrequires constant full engine speed operation even if power requirementsare low. Components have to be sized or a protective circuit such as anintermediate bus and capacitors or the like provided to accommodateover-voltages and prevent damage to the system.

Typical ring gear starter configurations for hybrid vehicles are noisy,and cranking speed is relatively slow. The starter motor adds cost andweight to the vehicle.

More consumers are desiring 110 or 240 volt output from the utilityvehicle so electrical tools can be operated and back-up house power canbe provided as necessary. Engine overload and engine stoppage,particularly upon initial loading of the electrical system, can be aproblem.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved hybrid utility vehicle. It is a further object to provide sucha vehicle which overcomes one or more of the aforementioned problems.

It is another object to provide a utility vehicle having an improvedsteering arrangement. It is a further object to provide such a vehiclewhich has improved drive arrangement.

It is yet another object of the present invention to provide an improvedhybrid utility vehicle. It is a further object to provide such a vehiclewhich facilitates better placement of vehicle components andattachments.

It is another object to provide an improved hybrid utility vehiclehaving improved power distribution structure.

In one embodiment of the invention, a hybrid utility vehicle includes atool-supporting frame and an electrical power source driven by anengine. Right and left rear wheels independently driven by permanentmagnet electric motors and front wheels electrically steerable over arange of approximately 180 degrees operate under the control of avehicle controller responsive to steering and speed input controls toprovide zero turn radius operation with minimum slippage and tirescuffing at varying vehicle speeds. Space efficiency provided by theelectric steering and an electrically driven tool deck facilitate avariety of tool mounting configurations including a rear discharge deckwith a chute passing under the vehicle frame between the driven wheels.The electric wheel motor drives are on the external side of the framerails, and the cut material conveying chute may be mounted much lowerthan is possible in a traditional lawn tractor layout which requireschute routing over a transmission. The hybrid construction eliminatesneed for a traditional transmission so the space can be used for movinggrass and other cut material to a rear hopper. Also, the material chutelocated in the middle rather than at a side of the machine facilitatestrimming. unhindered by discharge structure on either side of themachine.

An inverter connected to the electrical power source provides 110 and/or220 volt output for utility power use so hand tools and lawn tools canbe operated and back-up house power can be provided from the vehicle.The power source also functions as a high powered, high rpm, low noisestarter motor. The controller filters operator speed requests utilizinga torque control map. A control algorithm avoids engine overload andengine stoppage by causing electrical load to be taken from the batterypack and gradually applying generator load to allow governor to matchengine droop.

The hybrid vehicle can be operated from a battery pack when quietoperation is required. The vehicle 10 does not require hydraulic systemsand is particularly suited for operation in environments where oil leakspose a particular problem, such as on golf course.

These and other objects, features and advantages of the presentinvention will become apparent from a reading of the description whichfollows when taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of a hybrid utility vehicle withportions broken away to better show the component layout on the vehicle.

FIG. 2 is an enlarged top view of steerable front wheel structure onutility vehicle of FIG. 1.

FIG. 3 is a control system block diagram including an electronic vehiclecontroller for the vehicle of FIG. 1.

FIGS. 4A-4D show a logic flow chart for operation of the controller ofFIG. 3.

FIG. 5 is a logic flow chart showing shut-down procedure for the vehicleof FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, therein is shown a utility vehicle 10 such as ariding mower or other grounds care machine having a tool-carrying frame12 supported by right and left rear driven wheels 14 and 16 and frontsteerable wheels 18 and 20. A driven tool 24, shown in FIG. 1 as a mowerdeck, is supported from the underside of the frame 12 and includes aplurality of driven blade members 26 (FIG. 3) powered by electric motorstructure 26′. The electric motor structure 26′ may include a permanentmagnet dc motors 26′ individually driving each of the blade members 26or other suitable drive arrangement including but not limited to asingle motor driving the blade members 26 through a belt drive. Themotors 26′ can be “pancake” type motors to for more clearance on the topof the deck 24.

The frame 12 includes a rear frame portion 12 r on each side of thevehicle 10 supporting right and left integrated wheel motor assemblies34 and 36, each having a brushless permanent magnet dc motor 34′ and 36′and a planetary reduction gear structure 34 g and 36 g locatedsubstantially entirely outwardly of the rear frame portion 12 r andgenerally within rims 38 of the wheels 14 and 16. The construction ofthe rear frame portion 12 r and the compact wheel motor assemblies 34and 36 leaves a rearwardly opening accommodation space 40 between theassemblies and below the top of the rear frame portion 12 r unencumberedwith transmission or other wheel drive structure. A seat 42 is supportedfrom the top of the rear frame portion 12 behind an operator controlarea 46 and a hood area 48 which extends forwardly from the controlarea. A steering control 50 is located in the area 46.

An internal combustion engine 60 centered behind the front wheels 18 and20 is supported in the hood area 48. A combination starter/alternator 66is supported at the forward end of the engine 60 between the frontwheels 18 and 20 to generate electrical power using the engine 60 and toprovide high rpm, high torque engine starting at a low noise level. Inthe embodiment shown for a conventional lawn and garden tractor, theengine provides about fifteen horsepower and the alternator puts outabout thirteen kilowatts of power at full engine power from a threephase permanent magnet brushless generator. As a starter, the depictedstarter/alternator provides combustion engine cranking torque of greaterthan 40 Nm. It is to be understood that other engine/generatorcombinations and power outputs could be used.

A rectifier/inverter 68 (FIG. 3) is connected to the alternator whichoperates to boost generator voltage above the back emf of the generator.Current is injected into an inductance to provide the voltage increase.An output 70 is connected to a battery pack 74 and to bus 76 having abus voltage above 36 volts and typically about 42 volts. By operatingthe generator at an output level below the voltage on the bus 76 goodefficiency over a wide range of engine speeds is achieved without needfor a complicated voltage management scheme. With a back emf lower thanthe bus voltage, the electronics are designed to boost the generatoroutput up to the bus voltage. When generating, controller transistors inthe rectifier/inverter 68 are commutated 180 degrees out of phase frommotoring. The inductance of the machine thus adds the supply voltage tothe back emf voltage which raises the output over the bus voltage forcharging the batteries. The necessary bus voltage can be generatedefficiently over a wide range of engine speeds which allows running theengine at low speed for quiet operation when full power is not needed.The bus 76 is connected to an inverter 80 with an 110 volt or 240 voltoutlet 82 which can be conveniently located adjacent the accommodationspace 40 near the rear of the vehicle 10 for powering hand tools,providing emergency power to a building, and the like. The battery pack74 can be of thin film absorbed glass mat or other compact constructionwhich can be located adjacent the seat 42 near the inverter 80.

The front wheels 18 and 20 as shown in FIGS. 1 and 2 are steerablewheels movable over a range of about 180 degrees from a zero radiusright turn position to a zero radius turn left position. In FIG. 2, thewheel 18 is shown approaching the left-most turn position. The wheels 18and 20 are connected to a transverse axle member 90 for pivoting aboutupright axes (see 18 a in FIG. 2), and a steering linkage 92 generallyof the type shown and described in commonly assigned U.S. Pat. No.6,456,925 provides positive steering of the wheels through a rack andpinion structure 96. In one embodiment (FIG. 1), an electric motor 100powers the rack and pinion structure 96 and provides a drive by wirefunction which is independent of a mechanical linkage connecting asteering wheel directly to the steering linkage 92. Alternatively, aconventional mechanical steering linkage (not shown) can be providedbetween a steering wheel and the steering linkage 92 as described in theaforementioned Pat. No. 6,456,925 with the motor 100 acting as a powersteering assist if desired. Another type of drive by wire steeringcontrol is shown in FIG. 3 wherein, rather than using a single motor,separate electrically operated steering motors 108 and 110 independentlypivot the wheels about the wheel axes 18 a. For added traction andmaneuverability, the steered wheels 18 and 20 can be driven by compactmotors (location 18 h) or the like. In situations wherein steered frontwheels are deemed not to be necessary, the steering structure can beremoved completely so the wheels 18 and 20 simply caster and steeringcontrol is achieved as described below using full time independent driveof the wheel motor assemblies 34 and 36.

The compact arrangement of the wheel motor assemblies 34 and 36providing the relatively large accommodation space 40 facilitatesmounting of a rear material discharge chute 140 under the area of theseat 42 and generally under the frame 12. The chute 140 is connected tothe rear central portion of the mower deck 24. Since the drive structurefor the wheels 14 and 16 extends outwardly and away from theaccommodation space 40, the chute can have a more direct routerearwardly and chute size can be greater than with conventiontransmission systems. A cut material hopper 144 is shown connected tothe rear frame portion 12 r, and the chute 140 opens into the upperfront portion of the hopper 144. The rear discharge deck 24 facilitatesclose trimming on both sides of the vehicle 10. In addition, theconstruction permits transverse movement of the deck 24 for furthertrimming enhancement and more top deck clearance for improved tool lift.Electric actuators indicated generally at 150 in FIG. 1 provideimplement and tool lift and tool offset functions.

Referring now to FIG. 3, therein is shown an electronic vehiclecontroller 160 having a steering input 162 from the steering control 50,a speed command and direction input 164 from a foot pedal, and a brakecommand input 166 from a brake pedal. The pedals and steering control 50are located at the control area 46 and are shown to include variableresistors providing an analog voltage signal to the controller 160dependent on the selected position of each operator control. Thecontroller 160 also receives start and run signals from a key switchassembly 168 and engine speed and operating condition information vialines 170.

The vehicle controller 160 calculates the differential speeds of theright and left wheels 14 and 16 such that the vehicle can be steered andcontrolled with only differential traction drives and caster wheelswithout need to steer the wheels 14 and 16. The controller 160 thenoutputs a steering signal via lines 174 and 176 to the steering motors108 and 110, when the vehicle 10 is so equipped (or to a single steeringmotor if the steered wheels are mechanically linked for steering), tocontrol the positions of the steered wheels 18 and 20. Feedback lines178 and 180 (or a single line if a single steering motor is used)provide feedback signals to the controller 160 utilized primarily toverify that the steered wheels 14 and 18 are correctly positioned atvehicle start up. When the steerable wheels 18 and 20 are powered, thecontroller 160 provides speed control to the wheel drives depending onthe steering input at 162 and the foot pedal speed input at 164. Theright and left wheel motors 34′ and 36′ are connected to motorcontrollers 184 and 186 which received right and left wheel speedcommands from the controller 160 dependent also on the steering input at162 and the foot pedal speed input at 164. Speed and current feedbacksignals from the right and left wheel motors 34′ and 36′ are alsoinputted to the motor controllers at 194 and 196. The current feedbackis added to the basic control at 184 and 186 and enables vector controlif desired to enhance the control functions.

The steering and drive arrangement provides full time steerabledifferential drive wherein both rear wheels provide drive at all timesfor good traction characteristics. The vehicle turns well since thewheels are rotated at speeds matched to the requested turn angle. Thiscontrol of the individual wheel speed is accomplished without need for acomplicated and bulky spin steer transmission. When utilized with a 180degree or other short radius steering linkage, a high degree of vehiclemaneuverability is achieved. The controller 160 utilizes the steeringinput signal at 162 and the desired ground speed input at 164 from thefoot pedals to compute the correct wheel speed for the rear drive motors34′ and 36′. Further details of a control system for controlling thedriven wheels may be had by reference to the aforementioned U.S. Pat.No. 6,456,925.

The deck motors 26′ (FIG. 3) are controlled with a deck control switch206 connected to the controller 160. The controller 160 directs powerfrom the bus 76 to the motors 26′ when the switch 206 is closed. Aninverter switch 208 connected to the controller 160, when closed, turnson the inverter 80 so that power can be supplied through the outlet 82.The controller 160 filters operator speed requests at 164 utilizing atorque control map stored in controller memory. A control algorithmexecuted by the controller avoids engine overload and engine stoppage bycausing electrical load to be taken from the battery pack 74 asnecessary and gradually applying generator load to allow a governor onthe engine to match engine droop. If the engine 60 stops for any reason,the controller 160 initiates a shut-down routine (300 of FIG. 5). Uponindication at 301 of stoppage, right and left drive speed and torque areset to zero (302 and 303, respectively), and 120 ms delay is initiatedat 304. Thereafter, the ignition relay is set to off and the controlstate is returned to initialization.

Referring to FIGS. 4A-4D, a logic flow chart is shown for the operationof the controller 160. On turn-on of the vehicle 10, inputs are sampledat 400 to determine if there are any problems in the system or if aprevious error state has not been corrected, and if so (401), the stateis returned to Error at 402, an error message is provided at 403, andshutdown procedure is begun at 404.

Upon indication at 401 that no problems are detected, the state of thesystem is checked at 410. If the vehicle is in the initiation state,such as occurs at with normal start-up procedures, drive speeds are setto zero at 411 and interlock conditions such as brake on, speed controlin neutral and mower deck off are checked at 412. If all thepre-established conditions are met, the ignition relay is turned on at413 and the state of the key switch 168 is polled at 414. If the switchis in the start position, engine cranking is begun (415). If the switchis not in the start position, the alternator is disengaged at 416. Ifcranking is indicated at 410, key position is checked at 420, and ifstarting is indicated, the interlock conditions are checked at 421. Ifconditions are as prescribed, the starter is turned on at 422, agenerator speed is entered at 423. If the generator speed is sufficientfor providing proper voltage to the bus 76, the generator is activatedat 425 and the run timer is begun at 426. State is set to running at427.

If the key is not in the start position at 420, the starter is turnedoff at 430, and a two-second time out is established at 431. Generatorspeed is checked after two second at 432, and, if sufficient, powergeneration is begun at 433 and the state is set to running at 434 priorto the next pass through the routine. If at 421 it is determined thatnot all of the interlock conditions are met, the starter is turned offat 440, a short time-out delay is established at 441 after which theshutdown procedure is begun at 442. If generator speed has not reachedan acceptable level at 432 and generator speed is indicated to be belowa minimum speed at 451, the shutdown procedure is begun at 452.

Once the state at 410 is determined to be run, the drive to the wheelmotor assemblies 34 and 36 at full torque is commanded at 460 andvehicle conditions are checked (FIG. 4D). If the operator is properlypositioned relative to the vehicle at 461, the seat error flag iscleared at 462 and the deck switch 206 is polled at 463. If the deck ison and the deck flag is clear at 464, and if the foot pedal is in theneutral condition at 465, the deck is engaged at 466. If an overridecondition exists, such as mow in reverse switch has been activated(467), the deck override flag is set to true at 468. Otherwise, the deckoverride flag is cleared at 469. If the foot pedal is not in neutral at465 and if the foot pedal is in reverse at 470, the deck override flagis checked (471). If the deck override flag has previously been set totrue at 468 indicating a proper override condition exists, the deckengagement is enabled at 472. Otherwise, the deck is disengaged at 474and the deck error flag is set at 475. If the foot pedal is not inreverse (470), the deck override flag is set to false at 480 and thedeck is engaged at 481.

If at 461 it is determined that seat switch is off and at 483 (FIG. 4C)the vehicle brake is not engaged, shutdown is initiated at 484. If theseat switch is off (461) and the brake is on (483) the deck switch ispolled at 485 and, if off, the deck is disengaged (486) and the deckerror flag is set at 487. If the seat switch is on at 461 and the deckoff indication is received at 463, the error deck flag is checked at 488and deck override flag is checked at 489 before disengaging the deck at490. The steering algorithm 494 continues after condition checks.

Having described the preferred embodiment, it will become apparent thatvarious modifications can be made without departing from the scope ofthe invention as defined in the accompanying claims.

1-17. (canceled) 18: A hybrid utility vehicle including a frame forsupporting one or more tools, a combustion engine supported on theframe, an electrical power source driven by the engine, right and leftdriven wheels, steerable wheels offset from the driven wheels, thedriven wheels and steerable wheels supporting the frame for steeredmovement over the ground, wheel motor structure connected to the drivenwheels, electrically actuated steering structure connected to thesteerable wheels for moving the steerable wheel structure over a rangeof steered positions front a zero radius left turn position to a zeroradius right turn position, an electronic controller connected to thewheel motor structure and to the steering structure, a steering controlconnected to the electronic controller and providing a steering inputcontrol signal to the controller, the controller responsive to thesteering input control signal to operate the steering structure andcontrol the relative speeds of the driven wheels for increased wheeltraction and vehicle maneuverability and for decreased grounddisturbance at the left and right zero radius turn steered positions.19: The utility vehicle as set forth in claim 18 wherein the drivenwheels comprise rear wheels and the steerable wheel structure comprisesnon-driven wheels located forwardly or the rear wheels. 20: The utilityVehicle as set forth in claim 19 including a discharge chute connectedto the tools, the chute extending under the frame between the rearwheels. 21: The utility vehicle as set forth in claim 20 wherein thesupported tool comprises a mower deck supported between the drivenwheels and steerable wheels, the mower deck including a discharge chuteextending outwardly from the frame between the rear wheels. 22: Theutility vehicle as set forth in claim 20 wherein the supported toolcomprises a mower, the mower including a blade driven by an electricblade motor and connected to the electronic controller. 23: The utilityvehicle as set forth in claim 21 further including electric actuatorstructure connected to the mower deck for moving the mower deck relativeto the frame, wherein the electric actuator structure is located betweenthe drive wheels above the discharge chute. 24: The utility vehicle asset forth in claim 18 wherein the electrical power source comprises anelectrical power generator, wherein the generator also is operable as astarter for the combustion engine. 25: The utility vehicle as set forthin claim 24 wherein the generator is connected to an inverter providingan output voltage generally in a range of 110 to 240 volts to poweringan accessory, and further comprising a control connection between theelectronic controller and the inverter. 26: The utility vehicle as setforth in claim 24 wherein the generator drives the combustion engine ata speed greater than 600 rpm on engine start-up. 27: The utility vehicleas set forth in claim 24 wherein the generator has an output of greaterthan 10 kw and provides combustion engine cranking torque of greaterthan 40 Nm. 28: The utility vehicle as set forth in claim 18 wherein theelectrical power source comprises an alternator connected to a bushaving a bus voltage, wherein the back of the alternator is less thanthe bus voltage, and further comprising a voltage booster connectedbetween the alternator and the bus. 29: The utility vehicle as set forthin claim 18 wherein the one or more supported tools includes aselectively attachable cutting tool adapted for support between thesteerable wheels and the driven wheels, the cutting tool having adischarge chute adapted for support in a chute location between thedriven wheels, and wherein the inverter is located above the chutelocation. 30: The utility vehicle as set forth in claim 29 wherein thechute location is below the frame adjacent the wheel motor structure.31: The utility vehicle as set forth in claim 29 wherein the cuttingtool comprises a multi-blade mower driven by electric motor structureconnected to the power source and to the controller. 32: The utilityvehicle as set forth in claim 18 further comprising an operator speedcontrol connected to the electronic controller, and wherein control ofthe speeds of the driven wheels during vehicle turns is responsive tothe operator speed control. 33: The utility vehicle as set forth inclaim 18 further comprising feedback structure connected between thesteerable wheels and the electronic controller and providing a steerablewheel position indication to the controller. 34: The utility vehicle asset forth in claim 33 wherein the feedback structure provides an initialposition signal to the electronic controller at start up, the electroniccontroller responsive to the initial position signal to determine if thesteerable wheels are in a desired position. 35: The utility vehicle asset forth in claim 18 wherein the electrically operated steeringstructure is selectively removable from the steerable wheels to convertthe steerable wheels to non-steered caster wheels. 36: The utilityvehicle as set forth in claim 18 comprising an operator input steeringcontrol and an operator foot pedal speed control connected to theelectronic controller. 37: The utility vehicle as set forth in claim 18wherein the electrically operated steering structure comprises anelectric steering assist motor. 38: The utility vehicle as set forth inclaim 18 wherein the electrically operated steering structure comprisesa steer by wire structure. 39: A utility vehicle having a framesupported for forward movement over ground by front and rear wheels, thevehicle including an engine and an electrical power source driven by theengine, drive structure connected to at least one of the wheels andpowered from the engine for moving the vehicle over the ground wherevegetation is present, a deck supported by the frame and extendingtransversely to forward direction, a seat located rearwardly and abovethe deck, the deck including cutter structure for severing thevegetation and discharge structure providing a path for the severedvegetation, characterized in that the drive structure is offset to oneside of the discharge structure and the discharge structure is locatedsubstantially under the frame rearwardly of the engine to provide agenerally unencumbered path between the deck and a discharge locationoffset from the frame, wherein the cutter structure includes an electricmotor supported by the deck and connected to the electrical powersource, and the drive structure includes first and second electric drivemotors located on opposite sides of the discharge structure rearwardlyof the cutter structure, wherein the cutter structure includes twoelectric blade motors supported by the deck and connected to theelectrical power source, and the first and second electric drive motorsdefine a rearwardly directed accommodation space between the drivewheels for accommodating the discharge structure, and an electric toolactuator located in the accommodation space above the dischargestructure rearwardly adjacent the seat. 40-41. (canceled) 42: Theutility vehicle as set forth in claim 39 wherein the drive structure islocated on opposite sides of the frame outwardly of the dischargestructure 43-51. (canceled)